Protection of device from electrostatic discharge (ESD) damage

ABSTRACT

Embodiments of the invention relate to electrostatic discharge (ESD) protection. One embodiment includes a first dissipative adhesive (DA) connected to at least a portion of multiple leads in a first plane of a flexible cable in a coverage area for providing ESD protection to at least one element of an electronic device. A common bus bar is connected to the leads in a second plane of the flexible cable. Conductivity of the common bus bar is greater than conductivity of the first DA and the first plane and the second plane are different planes of the flexible cable.

BACKGROUND

Embodiments of the invention relate to electrostatic discharge (ESD)protection, and in particular, protection of a cabled device from ESDusing dissipative adhesive (DA) and a bus bar.

Magnetoresistive sensors (MR) and other devices that are sensitive toESD damage are often connected to a cable in order to electricallyconnect them to a device (such as a tape or disk drive) for operation.Such devices are extremely sensitive to ESD damage.

BRIEF SUMMARY

Embodiments of the invention relate to electrostatic discharge (ESD)protection. One embodiment includes a first dissipative adhesive (DA)connected to at least a portion of multiple leads in a first plane of aflexible cable in a coverage area for providing ESD protection to atleast one element of an electronic device. A common bus bar is connectedto the leads in a second plane of the flexible cable. Conductivity ofthe common bus bar is greater than conductivity of the first DA and thefirst plane and the second plane are different planes of the flexiblecable.

Another embodiment comprises a method for providing ESD protection to anelement of an electronic device. One embodiment comprises creating awindow for a plurality of leads in a first plane on a cable. In oneembodiment, a common bus bar is attached adjacent to the window in asecond plane on the cable. In one embodiment, a first dissipativeadhesive (DA) is applied across at least a portion of the plurality ofleads to connect the plurality of leads to one another and to the commonbus bar. In one embodiment, at least some leads of the plurality ofleads are operatively coupled to an element of an electronic device.

One embodiment comprises an ESD device. In one embodiment, a first DA iscoupled to a portion of leads on a flexible cable in a first plane ofthe flexible cable. In one embodiment, a bus bar in a second plane ofthe flexible cable is coupled to the leads via the first DA. In oneembodiment, conductivity of the bus bar is greater than conductivity ofthe first DA.

These and other features, aspects and advantages of the presentinvention will become understood with reference to the followingdescription, appended claims and accompanying figures.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 illustrates a schematic diagram of a simplified tape drive systemaccording to one embodiment;

FIG. 2 illustrates a side view of a flat-lapped, bi-directional,two-module magnetic tape head according to one embodiment;

FIG. 2A is a tape bearing surface view taken from Line 2A of FIG. 2;

FIG. 2B is a detailed view taken from Circle 2B of FIG. 2A;

FIG. 2C is a detailed view of a partial tape bearing surface of a pairof modules according to one embodiment;

FIG. 3 illustrates a schematic of a ladder structure for a dissipativeadhesive (DA) connection according to one embodiment;

FIG. 4 illustrates a schematic of connecting magnetoresistive sensors(MR) for an electronic device to a common bus bar according to oneembodiment;

FIG. 5 illustrates resistance data for DA connections without a commonbus bar, in accordance with an embodiment of the invention;

FIG. 6 illustrates a metal bus bar applied to a flexible cable, inaccordance with an embodiment of the invention;

FIG. 7 illustrates a 2.5% DA applied across a window of leads on aflexible cable, in accordance with an embodiment of the invention;

FIG. 8 illustrates a DA bus bar with 5% DA and 2.5% DA connecting leadson a flexible cable, in accordance with an embodiment of the invention;

FIG. 9 illustrates a circuit for a ladder structure, in accordance withan embodiment of the invention;

FIG. 10 illustrates discharge current data for the ladder circuit shownin FIG. 9, in accordance with an embodiment of the invention;

FIG. 11 illustrates a cable interfacing with a circuit board, inaccordance with an embodiment of the invention; and

FIG. 12 is a flowchart showing a process for applying a DA and a bus baron leads on a flexible cable, in accordance with an embodiment of theinvention.

DETAILED DESCRIPTION

The following description is made for the purpose of illustrating thegeneral principles of the present invention and is not meant to limitthe inventive concepts claimed herein. Further, particular featuresdescribed herein can be used in combination with other describedfeatures in each of the various possible combinations and permutations.

Unless otherwise specifically defined herein, all terms are to be giventheir broadest possible interpretation including meanings implied fromthe specification as well as meanings understood by those skilled in theart and/or as defined in dictionaries, treatises, etc.

Embodiments of the invention relate to electrostatic discharge (ESD)protection. According to an embodiment, a first dissipative adhesive(DA) connected to at least a portion of multiple leads in a first planeof a flexible cable in a coverage area for providing ESD protection toat least one element of an electronic device. A common bus bar isconnected to the leads in a second plane of the flexible cable.Conductivity of the common bus bar is greater than conductivity of thefirst DA and the first plane and the second plane are different planesof the flexible cable

FIG. 1 illustrates a simplified tape drive 100 of a tape-based datastorage system, which may be employed in the context of one or moreembodiments. While one specific implementation of a tape drive is shownin FIG. 1, it should be noted that the embodiments described herein maybe implemented in the context of any type of tape drive system.

As shown, a tape supply cartridge 120 and a take-up reel 121 areprovided to support a tape 122. One or more of the reels may form partof a removable cassette and are not necessarily part of the system 100.The tape drive, such as that illustrated in FIG. 1, may further includedrive motor(s) to drive the tape supply cartridge 120 and the take-upreel 121 to move the tape 122 over a tape head 126 of any type.

Guides 125 guide the tape 122 across the tape head 126. Such tape head126 is in turn coupled to a controller assembly 128 via a cable 130. Thecontroller 128 typically controls head functions such as servofollowing, writing, reading, etc. The cable 130 may include read/writecircuits to transmit data to the head 126 to be recorded on the tape 122and to receive data read by the head 126 from the tape 122. An actuator132 controls position of the head 126 relative to the tape 122.

An interface 134 may also be provided for communication between the tapedrive and a host (integral or external) to send and receive the data andfor controlling the operation of the tape drive and communicating thestatus of the tape drive to the host, all as will be understood by thoseof skill in the art.

By way of example, FIG. 2 illustrates a side view of a flat-lapped,bi-directional, two-module magnetic tape head 200 which may beimplemented in the context of one or more embodiments. As shown, thehead includes a pair of bases 202, each equipped with a module 204, andfixed at a small angle α with respect to each other. The bases aretypically “U-beams” that may be adhesively coupled together. Each module204 includes a substrate 204A and a closure 204B with a thin filmportion, commonly referred to as a “gap” in which the readers and/orwriters 206 are formed. In use, a tape 208 is moved over the modules 204along a media (tape) bearing surface 209 in the manner shown for readingand writing data on the tape 208 using the readers and writers. The wrapangle θ of the tape 208 at edges going onto and exiting the flat mediasupport surfaces 209 are usually between ⅛ degree and 4½ degrees.

The substrates 204A are typically constructed of a wear resistantmaterial, such as a ceramic. The closures 204B made of the same orsimilar ceramic as the substrates 204A.

The readers and writers may be arranged in a piggyback configuration.The readers and writers may also be arranged in an interleavedconfiguration. Alternatively, each array of channels may be readers orwriters only. Any of these arrays may contain one or more servo readers.Cables 205 couple the readers and/or writers 206 to a controller.

Tape heads with read, write, and servo elements exemplify the concept ofan electronic device with multiple elements requiring different diodetypes. For example, inductive writers do not require diode protection,and attaching diodes across the leads of a writer element will often bedeleterious to the writer performance, as the diodes will shunt currentaway from the writers, decreasing the writer currents for a givenapplied voltage/current. Often, servo and reader elements operate underdifferent current/voltage (IV) characteristics and thus requiredifferent diode designs. Therefore, a single diode chip which is capableof being used with a variety of magnetic head designs and could be wiredto the magnetic head in a particular way to avoid negative consequencesof attaching diodes across certain elements would be preferable.

FIG. 2A illustrates the tape bearing surface 209 of one of the modules204 taken from Line 2A of FIG. 2. A representative tape 208 is shown indashed lines. The module 204 is preferably long enough to be able tosupport the tape as the head steps between data bands.

In this example, the tape 208 includes 4-22 data bands, e.g., with 16data bands and 17 servo tracks 210, as shown in FIG. 2A on an example,one-half inch wide tape 208. Current linear tape-open (LTO) productsinclude 4 data bands and 5 servo tracks. The data bands are definedbetween servo tracks 210. Each data band may include a number of datatracks, for example 96 data tracks (not shown). During read/writeoperations, the readers and/or writers 206 are positioned within one ofthe data bands. Outer readers, sometimes called servo readers, read theservo tracks 210. The servo signals are in turn used to keep the readersand/or writers 206 aligned with a particular track during the read/writeoperations.

FIG. 2B depicts a plurality of readers and/or servos and/or writers 206formed in a gap 218 on the module 204 in Circle 2B of FIG. 2A. As shown,the array of readers and writers 206 includes, for example, 16 writers214, 16 readers 216 and two servo readers 212, though the number ofelements may vary. Illustrative embodiments include 8, 16, 32, 33, 40,64, 66, etc. readers and/or writers 206 per array. A preferredembodiment includes 33 readers per array and/or 33 writers per array, 32of which are used for forward and 32 for reverse tape motion. Thisallows the tape to travel more slowly, thereby reducing speed-inducedtracking and mechanical difficulties. While the readers and writers maybe arranged in a piggyback configuration as shown in FIG. 2B, thereaders 216 and writers 214 may also be arranged in an interleavedconfiguration. Alternatively, each array of readers and/or writers 206may be readers or writers only, and the arrays may contain one or moreservo readers 212. In some applications, a module comprises only readersand the writers are disposed on separate modules. For read-while writeverification for both forward and reverse tape motion across the readmodules when the readers and writers are on different modules, eithertwo reader modules surrounding one write module or two write modulessurrounding one read module are built into a head. As noted byconsidering FIGS. 2 and 2A-B together, each module 204 may include acomplementary set of readers and/or writers 206 for such things asbi-directional reading and writing, read-while-write capability,backward compatibility, etc.

FIG. 2C shows a partial tape bearing surface view of complimentarymodules of a magnetic tape head 200 according to one embodiment. In thisembodiment, each module has a plurality of read/write (R/W) pairs in apiggyback configuration formed on a common substrate 204A and anoptional electrically insulative layer 236. The writers, exemplified bythe write head 214 and the readers, exemplified by the read head 216,are aligned parallel to a direction of travel of a tape mediumthereacross to form an R/W pair, exemplified by the R/W pair 222.

Several R/W pairs 222 may be present, such as 8, 16, 32 pairs, etc. TheR/W pairs 222 as shown are linearly aligned in a direction generallyperpendicular to a direction of tape travel thereacross. However, thepairs may also be aligned diagonally, etc. Servo readers 212 arepositioned on the outside of the array of R/W pairs, the function ofwhich is well known.

Generally, the magnetic tape medium moves in either a forward or reversedirection as indicated by arrow 220. The magnetic tape medium and headassembly 200 operate in a transducing relationship in the mannerwell-known in the art. The piggybacked MR head assembly 200 includes twothin-film modules 224 and 226 of generally identical construction.

Modules 224 and 226 are joined together with a space present betweenclosures 204B thereof (partially shown) to form a single physical unitto provide read-while-write capability by activating the writer of theleading module and reader of the trailing module aligned with the writerof the leading module parallel to the direction of tape travel relativethereto. When a module 224, 226 of a piggyback head 200 is constructed,layers are formed in the gap 218 created above an electricallyconductive substrate 204A (partially shown), e.g., of AlTiC, ingenerally the following order for the R/W pairs 222: an insulating layer236, a first shield 232 typically of an iron alloy such as NiFe(permalloy), CZT or Al—Fe—Si (Sendust), a sensor 234 for sensing a datatrack on a magnetic medium, a second shield 238 typically of anickel-iron alloy (e.g., 80/20 Permalloy), first and second writer poletips 228, 230, and a coil (not shown).

The first and second writer poles 228, 230 may be fabricated from highmagnetic moment materials such as 45/55 NiFe. Note that these materialsare provided by way of example only, and other materials may be used.Additional layers such as insulation between the shields and/or poletips and an insulation layer surrounding the sensor may be present.Illustrative materials for the insulation include alumina and otheroxides, insulative polymers, etc.

One method of protecting magnetoresistive sensors (MR) is to connect allthe elements to a grounding wire which can then be connected to theground of the external device (e.g., a tester or a drive) prior toconnecting the elements directly to dissipate any voltage differentialsbetween the cabled device (CMOD) and the external electronics. Onemethod to connect the devices together is to apply a DA device acrossall elements. When the leads are side-by-side, then the resistance tothe grounding tab will be lowest for the lead closest to the groundingtab and highest for the lead the furthest away. Thus, the dissipationcurrents and times will be different for each element. One means ofsolving the problem is with a common bus bar. In some applications, thegeometry of the leads on the cable are such that in order to introduce acommon bus bar, the leads would need to pass into another layer in thestructure to make the connections. The leads and common bus bar,however, would both need to be exposed to an outer layer of the cable inorder to apply the dissipative adhesive. In many cases, there aregeometrical or functional restrictions on adding the leads on theavailable metal layers in the cable structure. For example, many cableshave a connector on the outer metal layer, and the connector precludespassing the leads to a common bus bar on the metalized layer used tosolder or otherwise connect the leads to the connector. Also, manycables used for high speed electrical signals on the leads have a groundplane on a layer either above or below the leads (e.g., an additionalmetal layer). In order to add the leads to the layer containing theground plane would require the ground plane to be disrupted, which canthen lead to noise pickup and the degradation of the performance of thedevice to which the cable leads are attached by decreasingsignal-to-noise ratio (SNR) of the device in operation. In other cases,the passing of the leads underneath other wires could also lead to noisepickup, especially with high frequency signals, and again a decrease inthe functional SNR.

In one embodiment, due to the geometry dilemma of multiple cable layers,a window is opened on the outer cover layer of the cable, exposing theleads, and a bus bar is attached to the outer surface of the cable nearthe exposed leads. This embodiment avoids crossing lines in the existingmetal layers and enables the application of the DA across the leads. Thecommon bus bar is in a different plane than that of the leads. In one ormore embodiments, since the DA is “fluid” when applied, the DA conformsto the different surfaces, electrically joining the leads in one planewith the common bus bar in the second plane.

One or more embodiments apply a bus bar on the surface of a flexiblecable. In one embodiment, the bus bar may comprise a metal strip or adissipative means with a higher conductivity than the dissipative meansused to connect the parallel leads attached to the sensitive devices(e.g., an MR). In one or more embodiments, placing the common bus barstrip on the external surface of the flexible cable eliminates the needto pass the leads into a separate layer and pass them underneath otherwire traces.

FIG. 3 shows a schematic of a ladder structure 300 for a DA connection,according to one embodiment. In one embodiment, the resistance to groundfor a track increases linearly with the distance to ground, and thecurrent through a given sensor (e.g., an MR) during a discharge ofconnecting the ground tab to an external ground will increase the closerthe element is to the grounding tab. In FIG. 3, in one example, Rmr isof the order of 100Ω, Rb is of the order of 7Ω, and Ra is of the orderof 100 kΩ. In one example, to first order, the sensor N from thegrounding tab will have a resistance-to-ground of N*Ra. With the ladderstructure 300, the currents passing through and the discharge times ofeach sensor along the ladder structure will be different.

FIG. 4 shows the schematic 400 of connecting the sensors to a common busbar. Taking the resistance Rg to be the direct connection from eachsensor to the common bus bar, to first order, the current to ground willbe To for all devices. The disadvantages of the ladder structure ascompared to the bus bar in schematic 400 may include Adj-Track is anorder of magnitude lower than Track-Gnd, wide distribution of track-gnd,discharge currents depend on location in the ladder, and no easy/obviousmeans of adding a common bus bar internal to the cable. Some of theadvantages of the bus bar over the ladder structure 300 may includetighter distribution of the track-gnd, track-gnd is closer to Adj-track,and discharge currents are the same for all tracks.

FIG. 5 illustrates resistance data without a common bus bar for DAconcentrations of 3% (A), 4% (B) and 5% (C). Table 1 shows observedresistances for a 3% DA. In one example, the internal resistances areall low at about 7.5 kΩ with a tight distribution. The resistance datashown comprises adjacent track data 510, internal track data 520,track-ground data 530 and servo-ground track data 540. In one example,the adjacent track data 510 is about seven (7) times higher with anaverage of about 50 kohm(Ω). The track-ground is eight (8) times higherstill at about 400 kΩ with a very wide distribution ranging from 100 to800 kΩ. The servo-Gnd graph 540 shows the servo-Gnd is about 10% of theTrk-Gnd data 530 at about 45 kn. The large variation in Trk-Gnd 530,Servo-Gnd 540 and Adjacent-track 510 make the implementation difficultin a manufacturing line where it is best to have these resistancessimilar.

TABLE 1 Resistances for DA with no common bus bar & 3% DA InternalAdj-trk Trk-Gnd Srv-Gnd Average (kΩ) 7.5 50 400 45 Max (kΩ) 7.5 80 80050 Min (kΩ) 7.5 40 100 30

FIG. 6 illustrates a device 600 including a metal bus bar 630 (e.g., acommon bus bar) applied to a cable 610 (e.g., a flexible cable), inaccordance with one embodiment. In one example, a metal bus bar 630comprises a copper (Cu) strip with a pressure sensitive adhesive (PSA)on the back side of the Cu strip. In other embodiments, othermetalalized PSAs may be used. In one example, the bus bar 630 isattached to the cable 610 near (e.g., adjacent, next to, etc.) a window640 exposing the leads (e.g., MR2 leads 651, MR1 leads 652, MR 16 leads655 (FIG. 7) ground wire 653, AC ground 654 (FIG. 7), AC ground 660,etc.).

FIG. 7 illustrates a device 700 including a 2.5% DA 750 applied acrossthe window 640 of leads on a cable 610, in accordance with oneembodiment. In one embodiment, a DA with 2.5% DA 750 comprising carboncontent was mixed up and applied across the window 640. In oneembodiment, the 2.5% DA 750 connects the leads to one another and to thebus bar 630. In one embodiment, a 2.5% DA 760 is applied across the ACground 660. In one example, Table 2 shows observed resistances for thedevice 700. In one example, all resistances are close to one another.

TABLE 2 Resistances for 2.5% DA with External Cu strip bus bar InternalAdj-trk Trk-Gnd Srv-Gnd Average (kΩ) 7.47 174 309 94 Stdev (kΩ) 0.01 2276 Max (kΩ) 7.49 202 403 Min (kΩ) 7.45 128 140

FIG. 8 illustrates a device 800 including a DA bus bar 850 with 5% DAand 2.5% DA 750 connecting leads on a cable 610, in accordance with anembodiment. In one example, device 800 shows an example of a highconductivity DA (5%) Bus bar and DA of 2.5% to connect the leads. In oneexample, the DA 750 and 850 are not continuous to the 2nd servo section810. The 2nd servo connection 810 is electrically connected to thegrounding tab via a 2.5% DA 760 and ACgnd (660)-5% DA-Gnd 860. Table 3shows observed resistances for the device 800.

TABLE 3 Resistances for 5% DA with External Bus Bar Internal Adj-trkTrk-Gnd Srv-Gnd Average (kΩ) 7.38 236 533 186 Stdev (kΩ) 0.37 43.7 156129 Max (kΩ) 7.50 304 751 277 Min (kΩ) 5.95 156 179 95

In one embodiment, the conductivity of the bus bar 630 is greater thanconductivity of the DA 750/850. In one embodiment, the bus bar 630 iscoupled to an outer surface of the cable 610. In one embodiment, themetal of the PSA tape of the bus bar 630 may comprise copper, aluminum,iron, etc. In one embodiment, the bus bar 630 may be deposited on thesurface of the outer layer of the cable 610 via deposition, such assputtering, chemical vapor deposition, electroplating, etc. In oneembodiment, the bus bar 610 may comprise a conductive paint. In oneembodiment, the bus bar 610 placement on the outer surface of the cable610 eliminates passing the leads into a separate layer and passing theleads underneath trace wires. If the concentration of carbon in thecommon bus bar 630 is too low, then it will be ineffective indistributing the charges along the length of common bus bar 630 and thecommon bus bar 630 will not function as required. If the concentrationof carbon is too high, then the viscosity of the carbon-polymer will betoo high to either mix homogeneously or possibly to even mix at all. Inone embodiment, the carbon mixture for the DA 750/850 may be in therange of 2.5% to 5%. In other embodiments, the percentage of carbon inthe DA mixture may be in other ranges, such as about 2%-6%, 1.7%-5.7%,etc. In one embodiment, a first DA (e.g., DA 750) comprises a compoundhaving carbon in a range of 2.0% to 3%, and a second DA (e.g., DA 850)comprises a compound having carbon in a range of 3.5% to 5%.

FIG. 9 illustrates a circuit 900 for a ladder structure, in accordancewith one embodiment. In one embodiment, Rmrj is the MR resistance, forexample 100Ω. In one embodiment, Ramn is the DA resistance between MR mto MR n, which is, for example 100 KΩ, where m and n are positiveintegers. In one embodiment, Rgnd is the resistance from Rmr4 to ground.In one embodiment, Cka and Ckb are the capacitance to ground for the kthMR element, where k is a positive integer.

FIG. 10 illustrates discharge current data 1000 for the ladder circuitshown in FIG. 9, in accordance with one embodiment. The dischargecurrent data 1000 shows that the charges accumulate for the MR elementscloser to ground as compared to the elements furthest from ground.

FIG. 11 illustrates a cable interfacing with a circuit board, inaccordance with one embodiment. In one approach, a DA grounding lead 712is provided with the cable 702, and the lead 712 may also be exposed bya window (e.g., window 640, FIG. 6), and may be coupled to a tab 714 forgrounding the DA (e.g., DA 750/850 once it is applied, thereby groundingelements of an electronic device. In one embodiment, this may beaccomplished by coupling the tab 714 to a ground on a circuit board 716,as shown in FIG. 11. There are various positions available for placementof the tab 714 as illustrated. Of course, the actual configuration andlayout of the cable 702 and the circuit board 716 may dictate whichplacement is preferred over another, according to some approaches.

In some approaches, the cable 702 may include a grounding lead coupledto a ground of the electronic device for grounding the at least oneelement of the electronic device through the DA 750/850. In furtherapproaches, the grounding lead may be an integral part of the cable 702located at least partially beneath a sheath covering the cable 702. Inone example, the grounding lead may run beneath a cable sheathing untilit reaches an end of the cable 702 at which point it may be exposed,thereby allowing the grounding lead to be grounded.

FIG. 12 is a flowchart showing a process 1200 for applying a DA (e.g.,DA 750) and a bus bar (e.g., bus bar 630, DA 850, Etc.) on leads on aflexible cable (e.g., cable 610), in accordance with one embodiment. Inone embodiment, in block 1210 ESD protection is provided to an element(e.g., an MR) of an electronic device by opening a window for aplurality of leads in a first plane on a cable (e.g., a flexible cable610). In one embodiment, in block 1220, a common bus bar is attachedadjacent to the window in a second plane on the cable which is differentfrom the plane containing the metal leads. In one embodiment, the planecontaining the metal leads and the plane containing the common bus baris separated by the outer cover layer of the flexible cable. In oneembodiment, the thickness of the cover-layer is 10 to 25 microns, so theseparation of the layer containing the leads and the layer containingthe common bus bar is of the order of 10 to 25 microns. In oneembodiment, the separation between the edge of one lead and the nextlead is of the order of 50 to 100 microns, so the vertical separationbetween the metal leads and the layer containing the common bus bar isof the same order of magnitude as the horizontal separation between theleads.

In one embodiment, in block 1230, a first DA (e.g., DA 750) is appliedacross at least a portion of the plurality of leads and the common busbar to connect the plurality of leads to one another and to the bus bar.In one embodiment, the designer of the process has the common bus baraligned in the process of block 1220 an appropriate distance away fromthe edge of the window on the cover layer to achieve the desired finalresistance between the leads and the common bus bar through the first DAdepending on the resistivity of the DA and the thickness of the DA, withall the appropriate tolerances taken into consideration. In oneembodiment, at least some leads of the plurality of leads areoperatively coupled to the element of an electronic device. In oneembodiment, the bus bar is coupled to an outer surface of the flexiblecable (e.g., a second plane), and conductivity of the bus bar is greaterthan conductivity of the DA. In one embodiment, the DA connects theplurality of leads to one another in a first plane and connects theleads to the bus bar in a second plane, and the bus bar comprises ametal, a metal PSA tape, a DA, a conductive paint, or other similarmaterials. In one example the metal or metal tape is deposited on thesurface of an outer layer (e.g., a second plane) of the flexible cablevia deposition comprising sputtering, chemical vapor deposition,electroplating, etc. In one embodiment, the element of the electronicdevice comprises a read transducer of a magnetic head.

In one embodiment, the DA is applied across exposed (e.g., via a window)leads on a first plane of a cable. In one embodiment, the DA may includea polymeric thin film, electrically conductive fillers dispersed in thepolymeric thin film, and a solvent for controlling a viscosity of theDA. In one embodiment, at least a portion of the solvent is evaporatedfrom the DA. The solvent enables the DA to form around the exposed leadsof the cable. In one approach, at least some of the leads may be coupledto an element of an electronic device. After the DA has formed aroundthe leads, the solvent may be evaporated out so that the DA obtains astructure similar to an elastomer, in one approach.

According to one embodiment, the DA may be applied via an applicationmethod selected from the group consisting of: syringing, silk screening,painting, and spraying. Of course, any other application method known inthe art may be used as well. In one approach, the solvent may be xylene,the polymeric thin film may be a polyurethane, and the electricallyconductive fillers may be carbon black. Of course, any other combinationof components may be used.

In one approach, the DA may have a viscosity in a range from about 10 CPto about 2000 CP prior to evaporation of the solvent therefrom, and morepreferably in a range from about 30 CP to about 250 CP prior toevaporation of the solvent therefrom, enabling the DA to flow around asurface area of the exposed leads of the cable in a coverage area. Thecoverage area is a portion of the exposed leads where the DA is applied.In one embodiment, the coverage area may be as close to 100% aspossible. In other embodiments, and as dictated by the particularapplication in which the DA is being used, the coverage area may begreater than about 95%, greater than about 90%, greater than about 80%,etc.

In another embodiment, the DA may have a lead-to-lead resistance in arange from about 50 kΩ to about 10 MΩ about 10 kΩ to about 100 MΩ, orany other range therebetween or as suited to the particular applicationfor which the ESD adhesive is being used.

According to some embodiments, MR sensor protection is immediate oncethe DA and bus bar are applied, which allows for the DA and bus bar tobe applied before the magnetic head is attached to the cable, providingprotection through the entire assembly process. In one embodiment, thematerials used in the DA and bus bar cause no physical change to thematerials used in the cable or the connector assembly. In oneembodiment, the low viscosity of the DA allows for increased surfacecontact with read and/or write transducer leads, thereby providingbetter protection than more viscous materials; if the viscosity of theESD adhesive changes, it may be returned to an original viscosity withthe addition of a common solvent; the low viscosity of the DA results indesired resistivities not achievable via other materials; the choice ofa polymeric material thinned by a solvent results in superior flowproperties while also providing a desired resistivity.

It will be clear that the various features of the foregoingmethodologies may be combined in any way, creating a plurality ofcombinations from the descriptions presented above.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, integers, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, integers, steps, operations, elements,components, and/or groups thereof.

It should be emphasized that the above-described embodiments of thepresent invention, particularly, any “preferred” embodiments, are merelypossible examples of implementations, merely set forth for a clearunderstanding of the principles of the invention.

Many variations and modifications may be made to the above-describedembodiment(s) of the invention without departing substantially from thespirit and principles of the invention. All such modifications andvariations are intended to be included herein within the scope of thisdisclosure and the present invention and protected by the followingclaims.

What is claimed is:
 1. An apparatus, comprising: a first dissipativeadhesive (DA) coupled to a portion of a plurality of leads that areexposed in a first plane of a flexible cable in a coverage area, thefirst DA provides electrostatic discharge (ESD) protection to at leastone element of an electronic device; and a common bus bar coupled to theportion of the plurality of leads via a second DA that is coupled overat least a portion of the first DA, the common bus bar disposed in asecond plane of the flexible cable, and the first DA electrically joinsthe portion of the plurality of leads in the first plane with the commonbus bar in the second plane, wherein conductivity of the bus bar isgreater than conductivity of the first DA, and the second plane is anouter layer cover of the flexible cable.
 2. The apparatus of claim 1,wherein coupling of the common bus bar to the portion of the pluralityof leads via the first DA and the second DA avoids crossing lines inexisting metal layers of the flexible cable, the first plane comprisesan inner layer of the flexible cable exposed via a window opening, andthe common bus bar is coupled to the outer surface of the flexiblecable.
 3. The apparatus of claim 1, wherein the first DA connects theplurality of leads to one another.
 4. The apparatus of claim 2, whereinthe common bus bar comprises a metal, wherein the metal is deposited onthe flexible cable via one of sputtering, chemical vapor deposition orelectroplating.
 5. The apparatus of claim 2, wherein the common bus barcomprises a conductive paint.
 6. The apparatus of claim 2, wherein thecommon bus bar comprises a metalized pressure sensitive adhesive (PSA)tape.
 7. The apparatus of claim 1, wherein the common bus bar placementon the outer surface of the flexible cable eliminates passing theplurality of leads into a separate layer and passing the plurality ofleads underneath trace wires.
 8. The apparatus of claim 1, wherein theat least one element of the electronic device is a read transducer of amagnetic head.
 9. The apparatus of claim 1, wherein the first DAcomprises a compound having carbon in a range of 2.0% to 3%.
 10. Theapparatus of claim 1, wherein the second DA comprises a compound havingcarbon in a range of 3.5% to 5%.
 11. The apparatus of claim 1, whereinthe common bus bar is electrically coupled to a grounding tab.
 12. Anelectrostatic discharge (ESD) device, comprising: a first dissipativeadhesive (DA) coupled to an exposed portion of leads in a first plane ofa flexible cable; and a bus bar in a second plane of the flexible cablecoupled to the exposed portion of the leads via the first DA, and atleast a portion of the first DA is coupled over at least a portion ofthe bus bar, wherein the second plane is an outer layer cover of theflexible cable and conductivity of the bus bar is greater thanconductivity of the first DA.
 13. The ESD device of claim 12, whereinthe first DA electrically connects the bus bar to the exposed port ofthe leads, and the bus bar comprises one of: a second DA, a metal, aconductive paint and a metalized pressure sensitive adhesive (PSA) tape.